Air flow control for underfeed stokers



March 7, 1939. H. C. CARTER AIR FLOW CONTROL FOR UNDERFEED STOKERS 3Streets-She#v Filed Feb. 4, l 1935 ENTER H.C .C.AQ.TE12 5% /4 7' TUR/v5v/ March 7, 1939. H. C. CARTER AIR FLOW CONTROL FOR UNDERFEED sTOKERsFiled Feb. 4, l1935 3 Sheets-Sheet 2 MME/v TD R H. C CARTER 'March 7,v1939.

-H. C. CARTER AIR FLOW CONTROL FOR UNDERFEED STOKERS Filed Feb. 4, 19353 Sheets-Sheet 3 .ha e m m Z Ow N w.. n w N L 1h11 ng m QJ ssAlH.C..CAF2TE2 I/JTrURA/EV Patented Mar. 7, 1939 UNITED STATES AIR. FLOWCONTROL FOR UNDERFEED STOKERS Haskell C. Carter, Portland, Oreg.,assignor to Iron Fireman Manufacturing Company, Portland, Oreg.

Application February 4, 1935, serial No. 4,945

23 Claims.

This invention relates generally to underfeed stokers, and particularlyto an air flow control therefor.

The main object of this invention is the pro- Vision of an air controlwhich will insure a uniform or constant volume of air flowing throughthe air duct during the entire time fuel is being fed by the stoker.

, 'I'he second object is to construct an air control for coal stokerswhich will beoperated by static and velocity pressures, in other words,by total pressure.

The third object is to provide a simple, inexpensive and highly eicientform of control which will automatically correlate Athe air and fuelfeeds regardless of variations in the resistance offered by the fuel beditself.

I accomplish these and other objects in the manner set forth in thefollowing specification as illustrated in the accompanying drawings, inwhich:

Fig. 1 is a perspective of a with my device.

Fig. 2 is a fragmentary side elevation with the actuating cylinderbroken away in vertical section. y

Fig. 3 is a section taken along the line 3--3 in Fig. 2.

Fig. 4 is a section taken along the line 4-4 in Fig. 3 showing theposition of the valve when the fan is not being operated.

Fig. 5 is a View similar to Fig. 4 showing a posittin of the valve whenthe fan is being oper-y a e Fig. 6 -s a fragmentary view of a modifiedform of the device showing the actuating cylinder and portion of tle airduct in vertical section and showing the parts set for automaticoperation.

7 is a section taken along the line 'I-1 in Fig.

Fig. 8 is a section taken along the line 8-8 in Fig. 6.

Fig. 9 is a section taken along the line 9 9 i Fig. 6.

Fig. 10 is a perspective View of a modified form of the device in whichthe control is applied to the air inlet of the stoker fan.

Fig. 11 is a brokenI horizontal section taken along the'line II--II inFig. 10.

Fig. 12 is a. section taken along the line I2-I2 in Fig. 11,y showingthe valve in its position with the fan stopped.

Fig. 13 is a view similar to Fig. 12 showing the valve in a positionwith the fan operating.

stoker equipped (Cl. 11o-6.9)

Fig. 14 is a section taken along the line I4-I4 in Fig. 12.

Fig. 15 is a section taken along the line I5-I5 in Fig. 2.

Similar numbers of reference refer to similar i parts throughout theseveral views.

Referring in detail to the drawings, in the form of the device shown inFigs. 1 to' 5 inclusive, there is shown a retort I5 to which fuel issupplied from a hopper IB through a fuel tube I'I by means of a worm I8,which is driven by a motor I9 through a transmission 20. A fan (notshown) is disposed within the fan casing 2l, which is connected by theair duct 22 to the plenum chamber 23 around the retort I5. It will beunderstood that the transmission is preferably of the variable speedtype. r

Referring particularlyA to my invention, it will be seen that there ismounted on the duct 22 a standard 24, which supports an upright cylinder25, whose head 26 is provided with a vent 21. Within the cylinder is adisk 28 which serves as a loose piston, same being mounted on the pistonrod 29 which is slidable within the piston head 30 and in the base 3l ofthe standard 24. Attached to the lower end of the piston rod 29 is amain control damper 32 which completely closes the duct 22 when thepiston 28 is in its lowermost position or opens it in proportion to theamount the piston 28 is raised.

Mounted in the air duct 22 between the fan. casing 2| and the maincontrol damper 32 is a pilot vane 33, which is secured to the rockableshaft 34 which journals in the sides of the air duct 22. The shaft 34projects through a valve body 35 and also through a perforated plate 36,whose perforated portion 3IV occupies a slot 38 in the valve body 35. Ahole 39 passes through the valve body 35 and can register with theopening 40 in the plate portion 31. It is desirable to provide a stop 4Ion the plate portion 31 to limit the opening movement of the valve to afull open position when the fan is stopped.

On the square end 42 of the shaft 34 is mounted an indicator arm orpointer 43 and the duct 22y is provided with a series of marks 44 bymeans of which the pointer 43 can indicate the position of the pilotvane 33. In order that the position of the plate 36 may be adjusted withrelation to the indicator arm 43 and the pilot vane 33, there isprovided a clamp 45, which is held by means of a wing nut 46. 'I'he pin4I makes it very convenient to adjust the relationship of the plate 3Swhich is loose on the round shaft 34 and the indicator arm 43 which ison a square portion 2 of the same shaft because when the plate is pushedupwardly around its pivot the holes 39 and 48 are brought into registryaltho these cannot be seen from the outside. The damper 33 is raised thedesired amount by lifting the pointed end of member 43 until the settingis such as to obtain the desired fixed volume of air. The graduations 44make it convenient to position the damper correctly and with the plateheld so that the pin 4| is in contact, the thumb nut 46 is tightenedwhich has the effect of rigidly fastening together the plate 36 and thepointer or indicator arm 43 so that these two thereafter move as a unit.The hole 39 in the valve body 35 is connected by means of a pipe 41 tothe lower end of the cylinder 25. Communicating with the inner end ofthe hole 39 is a street L 48, whose open end 49 faces the fan. f

The operation of this form of the device is as follows:

With the parts in the position shown in Fig. 2, that is with the fan notoperating, the main control damper 32 is in its lowermost position inwhich it serves as a banking damper prevent- .ing air from reaching thefuel bed as a result of the natural draft. Now assuming that the fan isoperated, it is evident that at first there will be no flow of air pastthe main control damper 32 and therefore the pilot vane 33 will not bemoved, and pressure will be built up in the air duct 22 between thedamper 32 and the fan, and since the hole 39 registers with the opening48, as shown in Fig, 4, air will pass through the pipe 41 into thecylinder 25 on the underside of the piston 28 causing it to rise and tocarry with it the main control damper 32.

Obviously, the air within the cylinder 25 above the piston 28 must bedisplaced, and it escapes through the vent 21 giving a cushioning actionto the upward movement of the piston 28. As

the damper 32 opens, air flows past the pilot vane,

. 33, causing it to rise and to move the plate 36 toa position similarto the one shown in Fig. 5, that is moving the hole 39 and the opening40 out of register and restricting the flow of air to the cylinder 25.Owing to the fact that there is an appreciable clearance around thepiston 28, air can pass around same and escape through the vent 21 tothe atmosphere, thus permitting the piston 28 to descend making itpossible to secure a state of balance between the parts.

In other words, for a given setting between the pilotuvane 33 and theplate 36, a relatively fixed volume of air will be delivered by the fanto the combustion chamber regardless of the resistance offered by thefuel bed.

In the form of the device shown in Figs. 6 to 9 inclusive, the pistonrod 29 is joined by a link 50 to a butterfly main'control damper 5|,which is pivotally mounted on the shaft 52, which journals in the sidesof the air duct 22 and has secured on its outer endV by means of a key53 a slotted arm 54, which is capable of being clamped in a desiredposition by means of the wing nut 55 on the stud bolt 56. The arm 54 isgraduated to facilitate the desired non-automatic setting of thebalanced damper 5|, an index 51 being provided on the block 58. The wingnut 55 is normally loosened in the automatic operation of the control sothat themovement of the balanced damper 5| and the"arm 54 which moveswith it shall be under control of the piston 28.

In this form of the device, the pilot vanev59 is hingedly mounted on theshaft 68, which journalsinthesidesoftheairductnandinthe valve body 6|.In thevalve body 6| is formed an L-shaped passageway 62, whose inner endis connected to a street L 63, which is within the duct 22, whose openend 64 faces the fan. 'I'he outlet 65 of the passageway 62 is normallyclosed by the valve 66 which consists of the inturned end of the valvearm 61, which is rotatable on the shaft 68.

Keyed on the shaft 68 is an indicator arm 68, which is provided with anarcuate slot 69 within which is disposed the bolt 18, which is held bythe valve 61. The bolt 18 is provided with a wing nut 1I. The indicatorarm 68 is graduated and the valve arm 61 is provided with an index mark12 to facilitate the setting of the arm 68 to a desired relationshipwith` the valve arm 61. The passageway 62 communicates by means of apipe 13 with the lower end of the cylinder 25.

The operation of this form of the device is quite similar to that shownin Figs. 1 to 5, except that in this form of the device the main controldamper 5| is balanced, thereby facilitating the koperation thereof andalso that .when a static head is built up 'within the duct 22 betweenthe main control damper 5| and the fan itself, air enters the street L63 and passes through\the open pipe 13 to the cylinder 25, therebycausing the main control damper 5| to open and per. mitting air to flowpast the pilot vane 59 and utilizing its velocity to raise same, causingthe valve 66 to open and air to waste to the atmosphere as thisvalveturns about its pivot which is the shaft 68, again permitting theestablishment of a balance between the volumes of air and fuel deliveredas determined by the static head within the duct 22 and also on thevelocity of the air passing through the duct 22.

In the form of the device shown in Figs. 10 to 14 inclusive, the retort14 is connected to the fan casing 15 by means of an air duct 16.' Inthis form of the device, the fan 11 is provided with two inlet openings18 and 19, which are in series and spaced from each other. Between theopennsy ings 18 and 19 is disposed a fan damper 88, which may closeeither of these two openings. While it normally closes the opening 19,as illustrated, when the fan is not operating; upon the building up ofexcessive pressure in the flexible bag '86, it is forced toa position toclose the opposite opening 18 so as to shut off the supply of air to thefan or blower 11. The damper 88 is mounted on the slidable rod 8|, whichis actuated by the dia.- phragm 82, which is connected by means of thevalve control pipe 83 with the valve body 35, the parts of which areidentical with those described in Figs. 3 to 5 inclusive. The diaphragm82 is urged toward a collapsed position by means of the spring 84 and isprovided with a shorter spring 85 to enable the fan damper 88 vto openagainst the vacuum produced by the fan 11. Thus it will be seen that thediaphragm 82 will rise relatively quickly, when the fan 11 is startedbut will move very much slower when the shorter spring 85 is engaged asat such time the upward movement of the diaphragm 82 is resisted by bothof the springs.

'It will be noted that the flexible bag 86, of which the diaphragm 82forms a part, is supported by the cage 81,through whose side open-l ings88 air can pass through the openings 19 and 18 into the fan'll. It isdesirable to provide a valve 89. It will be noted that in this form ofthe device, the control of the air flow is made at the fan inlet, whilein the previously described forma, it is made in the air duct itself.

In this form of the device, when the fan 11 is not operated, the spring84 will move the damper 88 to close the opening 19, causing same toserve as a banking damper. If, however, the Stoker motor is operated inresponse to any of its controls, the fan 11 is operated and the partialvacuum produced in the casing 15 unseats the fan damper permitting airto be drawn into the casing 15 and discharged into the duct 16. The airfromthe fan 11 enters the street L 48, as shown in Fig. 11, and as theair from the fan 11 flows past the pilot vane 33-A, causing same torise, the hole 39 and opening 48 are brought into register, as shown inFig. 13, permitting air to flow through the pipe 83 ino the bag 86 andovercoming the spring 84 and gradually increasing the restriction to theflow of air through the opening 18. Obviously, the speed of thisoperation can be controlled by the setting of the valve 89.

While in this form of the device, the arrangement of the parts issomewhat different than those in the two forms previously described, theprincipal difference is in the location of the control point, namely atthe fan inlet opening. It will be noted that in all of the forms of thisdevice, herein illustrated and described, total pressure is utilized tomaintain the correct air flow, and at the same time the velocity of theair is utilized resistance of flow 0I" air through the duct, a

pneumatic actuator for said main control damper, a pilot vane responsiveto velocity of ilow of air and located within said duct between said airsupplying means and the main control damper, an air pipe extending fromsaid pneumatic actuator to the interior of said air duct and having anintake opening facing in the direction of ,said air supplying means anda valve actuated by said pilot vane for controlling the flow of airthrough said air pipe to said pneumatic actuator, whereby an increase ofvelocity of air past the pilot vane will cause the valve to lessen theiiow of air through the air pipe so the actuator will move the maindamper to restrict the ow .of air to the Stoker, thus maintaining auniform volume of air flow to the Stoker.

2. In an underfeed stoker the combination of a retort, an air duct forsupplyingair to said retort, a main control damper disposed within saidduct, a pneumatic actuator connected to move said control damper to openposition in response to air pressure in the duct, a pilot vane disposedwithin said duct, a valve connected to be actuated toward closedposition by said pilot vane as the vane 'moves in response to airvelocity, and an air pipe communicating by way of said valve betweensaid pneumatic actuator and the interior of said duct whereby as thevelocity of the air increases the opening of the valve decreases therebyallowing the main control damper to restrict the air flow.

pneumatic 'actuator operable by said pilot vane to close said damper inproportion to the velocity of air in the duct and an adjustable indi- 10cator for varying the relationship between said pilot vane and valvesetting.

4. In an underfeed stoker the combination of an air duct, a main controldamper disposed Within said duct, a pneumatic actuator for said 15damper, a pipe for supplying air from said duct to said actuator,l meansfor retarding the operation of said actuator, means for varying the owof air from said duct to said actuator, said last mentioned meansconsisting of a pilot vane actuating valve whereby an increase in the owof air past said pilot vane will increase the restriction to the flow ofair to said pneumatic actuator.

5. A device of the class described characterized by having a pilot vaneresponsive to the velocity of air owing through an air duct, a maincontrol damper responsive to the flow and static head of the air passingthrough said duct, means actuated by the pilot vane for rendering thecontrol damper less responsive to air flow and means for varying therelationship of said damper and vane and for indicating the relativepositions of said damper and vane.'

6. In a device for regulating the ow of air to the retort of anunderfeed stoker so as to insure the delivery of a constant volume ofair per unit of time for combustion; an air supply duct, a f devicegoverning the ow of air through said duct, pressure actuated meansresponsive to pressure in said air duct for operating said device toalter the resistance offered to the flow 0f air through said duct, andmeans including a vane within the duct for regulating the pressuretransmitted to said pressure actuated means in inverse ratio to thevelocity of air ow through the duct.

7. 'Ihe device of claim 6 in which the vane is pivoted within the ductso as to be moved in accordance with the velocity of the air owing andsaid last named means including a. bleeder valve movable with the vaneto control the pressure transmitted to the pressure actuated means.

8. In a device for regulating the flow of air from the fan to the retortof an underfeed stoker so as to insure the supply of a constant volumeof combustion air per unit of time; an air supply ducnleading from thefan to the retort, amain control device movable to restrict the ilowthrough said duct, pneumatic means for moving said device, a passagewayconnecting the pneumatic means with the interior of the air duct, avalve for controlling the flow of air through said passageway and meansmovable in response to changes in velocity of air Within the duct forcontrolling the position of said valve, said means being responsive to alesseningof velocity of air in the duct from normal flow to move thevalve to position to cause the main control device to open further andwhich means in response to an increase in velocity from normal ow willcause a movement of the device toward a closing position. 70

9. In an air supply means for feeding combustion air under pressure tothe retort of an underfeed Stoker; an air duct, a main control damperconstantly urged to banking position, a pneumatically operated memberfor moving the the supply of air from the blower to the chamber,l

' damper in opposition to said urge, a passageway leading from the airduct to said member to move the member so as to open the damper,ya valvefor modifying flow through said passageway, a pilot vane pivoted in saidduct so as to be moved in accordance with the velocity of air flowing,and means adjustably connecting the vane and the valve so that thedamper and the vane assume relative positions when air is flowing and anincrease in velocity of the air causing a relative closing of the maincontrol damper.

10. In combination, an air duct, a device for restricting or closing theduct, pneumatic means responsive to pressure Within the duct for movingthe device toward open position, and valved means g governed by thevelocity of flowfor modifying the pressure transmitted to the pneumaticmeans in inverse proportion to the velocity' of ow.

11. In a device for regulating the flow of air from the fan to theretort of an underfeed stoker so as to insure the supply of a constantvolume of `combustion air per unit of time: an air supply duct leadingfrom the fan to the retort, a. banking damper constantly urged to aposition to close said duct, pneumatic means for moving said dampertoward opening position, a passageway connecting said pneumatic meanswith the inling volumetrically the admission of air to the flow of airthrough said passageway and means movable in response to changes invelocity of air within the duct for controlling the position of said cvalve whereby when air is flowing in normal operation a lessening ofvelocityA of air in the duct will move the valve to position to causethe damper to open further and an increase in velocity will cause amovement of the damper toward closing position.

12. The device of claim 11 in which the velocity responsive meansincludes a vane in said duct.

13. The device of claim 11 in which the velocity responsive meansincludes a vane insaid duct and the valve is adjustably secured to movewith the vane and bleeds the passageway to the atmosphere as the vanemoves toward closed position.

14. In fuel burning apparatus having a fuel support and an air chamberfor supplying air thereto, the'combination of a blower operable to feedair into said chamber, a damper for controlling volumetrically theadmission of air from the blower to the chamber, said damper tendingnormally to assume a closed position to shut off a movable regulatingdevice disposed outside the air chamber and operatively connected withthe damper, and means for rendering air pressure from said chamberefftive on said movable regu- 'lating device to move said damper to openpositions.

15. In fuel burning apparatus having a fuel support and an air chamberfor supplying air thereto, the combination of a blower operable to feedair into said chamber, a damper for controlling volumetrically theadmission of. air to the blower, said damper tending normally to assumea closed position, a movable regulating device 1 disposed outside theair chamber and operatively connected with the damper, and means forrenderingair pressure from said chamber effective on said movableregulating device to move said damper from said closed position upon anincrease in pressure in said air chamber and to move the damper torestrict the iiow of air to the blower when the pressure exceeds achosen amount.

16. The device of claim 15 in which the damper moves between two spacedinlet openings in series.

17. The device of claim 15 in which the damper is spring pressed toclose an outer inlet opening but may move against said spring to closean inner inlet opening in series with the outer inlet opening,.andthereis a second spring not engaging the damper when closing the outer inletopening but which resists movement of the damper when approaching theinner inletopening.

18. In fuel burning apparatus having a fuelA support and means forfeeding fuel thereto, the combination of a blower, a conduit forconducting air from the blower to the fuel support, a damper forcontrolling admission of air to the blower,

.said damper tending to assume a closed position when the blower is notoperating, and regulating means operable by air pressure in the conduitto move the damper from said closed position upon an increase inpressure in the conduit and to move the damper to shut olf air to theAblower uponA .I

stoker, an air duct, means for creating a ow ofY air through said duct,a damper movable to modify the iiow of air through the duct, a pilotmember within the duct and movable in accordance with the velocity ofthe air moving in said du,ct,.V

and means cooperating with said pilot member to aiect the position ofthe damper, whereby when the flowcreating means is iirst caused tooperate it builds up a pressurein the duct, moving the damper to aposition to increase the flow of air,

through the duct in proportion to the degree ofpressure within the duct,and when in normal operation the position of the damperis controlled bythe pressure withinthe duct as modified by the Y velocity of flow of airin the duct.

22. The device of `claim 21 in which the damper moves to closed positionto act as a banking damper when the flow ceases.

23. The device of claim 21 in which the damper moves between two inletopenings, closing one of said openings when the ilow ceases so as to`act as a banking damper, and covering the other of f said openingsWhenever the pressure in the duct exceeds a chosen amount.

HASKELL C. CARTER.v

